Amiga E is a programming language and compiler I started creating for the Amiga in '91, released publicly in '93, and released as open source in '97. It was most similar to C++, in the sense that it was fast and weakly typed, and had a rich set of features from procedural, object oriented and functional programming languages.

I wrote the entire thing in assembly language, which will always persist in my mind as the craziest software engineering exercise I have ever gone through (400kb of mostly uncommented assembly in a single source file, for a complex compiler).